The order, valued at a combined $2.8 billion at current list prices, will make Etihad the world's largest airline customer of the 787-9.
Etihad has a total of 41 787s on order.
The order also increases Etihad's current Boeing 777 backlog to 12 planes, which includes 10 previously ordered 777-300ERs (extended range).
The Abu Dhabi-based airline's fleet currently includes eight Boeing 777-300ERs and one 777 Freighter.
"Our decision to expand our Dreamliner fleet is testimony to Etihad's commitment to operating one of the youngest and most fuel efficient fleets in the skies," Etihad Airways Chief Executive Officer James Hogan said.
"It also reflects our confidence in the 787's ability to have a significant impact on our operating efficiencies and the passenger experience we can offer onboard this revolutionary aircraft. Both the Boeing 787 Dreamliner and the 777 Freighter offer highly attractive operating economics and will facilitate our global expansion plans by allowing us to transport passengers and cargo into new global markets from our hub in Abu Dhabi."
Founded in 2003, Etihad Airways is one of the fastest growing airlines in the world and currently operates scheduled flights to 84 passenger and cargo destinations across Europe, Middle East, Africa, Asia Pacific and North America.
"In less than 10 years Etihad Airways has established an enviable track record and has earned global recognition for its focus on providing its customers with a quality product," said Jim Albaugh, CEO, Boeing Commercial Airplanes.
"We are extremely proud of our partnership with Etihad Airways and are confident the 787 Dreamliner and the 777 Freighter will make valuable contributions to Etihad's growth plans and service to its passenger and freight customers."
The Boeing 787 Dreamliner is an all-new commercial jetliner that brings new efficiencies to airlines and delivers superior comfort to passengers.
The Dreamliner is the fastest-selling twin-aisle airplane in aviation history, with more than 800 orders from 58 customers around the world.
The 777 freighter is the world's longest-range, twin-engine freighter and features the lowest trip cost of any large freighter, with high-cargo density and 3.1-meter interior height capability that complements the popular 747 freighter family.
